This project aims to identify new chromosomal susceptibility loci for familial colorectal cancer. Probands and their relatives are evaluated on the GCRC, utilizing the newly constructed research endoscopy facilities. Mapping of new colon susceptibility genes through linkage analyses has identified several new candidate loci. The Colon Cancer Risk and Prevention Clinic has enabled investigators to assemble over 2,000 index cases and over 50 pedigrees have been evaluated in depth.